The present invention is directed to improved ethylene-alpha-olefin elastomers, especially EPDM-based elastomers, for use in manufacturing power transmission products, such as power transmission belts, timing belts, and the like. More specifically, the invention is directed to such elastomers which incorporate certain types of functionalized polyethylenes which result in belts having enhanced physical properties.
Power transmission belts are known. See for example, U.S. Pat. No. 6,561,937 (Wegele); U.S. Pat. No. 6,695,734 (Hedberg et al); U.S. Pat. No. 5,610,217 (Yarnell et al) and U.S. Pat. No. 6,251,977 (Georget et al). Proposals have already been made on numerous occasions to use EPDM (ethylene propylene diene terpolymer) elastomers cured by organic peroxides in the manufacture of power transmission belts, because of the qualities and advantages of such elastomers such as cost, operating temperature range, and ability to withstand oxygen and ozone, such EPDM-based elastomers having additives which improve their dynamic properties such as resistance to fatigue and to wear, their breaking strength, and their modulus of elasticity, and also their adhesion to traction cords, which additives are generally constituted by metallic salts of α,β-unsaturated organic acids (in particular zinc methacrylate) plus reinforcing fillers such as carbon black and possibly fibers, e.g. aramid fibers. For example, the Yarnell '217 patent teaches the use of α,β-unsaturated organic acids in peroxide cured EPDM elastomers. The Georget et al '977 patent teaches the inclusion, in peroxide cured elastomers, of an elastomer grafted with maleic anhydride which reacts with the α,β-unsaturated organic acid metallic salt included in the composition to reinforce the curing of the EPDM-based elastomer and to improve its dynamic characteristics, such as in particular its modulus of elasticity, its breaking strength, and its hardness. The elastomer grafted with maleic anhydride can be a polybutadiene, polyisoprene, polypropylene, or an ethyl vinyl acetate (EVA) copolymer, and the elastomer is used as a power transmission belt.
Oxidized polyethylenes are known and are taught by U.S. Pat. Nos. 2,683,141 and 3,060,163 to Erchak. They are used to form stable, translucent emulsions for use in floor waxes, in coatings for asbestos shingles, paper and textiles, and in inks for application to various surfaces. They have been incorporated into thermoplastic polypropylene compositions containing EPDM compositions, such as those described in U.S. Pat. No. 4,990,568 to Benefield et al. In Benefield a thermoplastic polypropylene is modified with EPM or EPDM and an oxidized or carboxylated polyolefin, in at an amount of 2 to 20% of the elastomer, to improve the problem of adherence of coatings applied to the surfaces of articles formed from the thermoplastic elastomers.